Field of the Invention
This invention relates to a device for the generation of ozone and to a process for its operation.
Discussion of Background
A conventional ozone generation device representative of the state of the art is known from German Offenlegungsschrift No. 2,111,041.
There are two main possibilities of electrical supply for high-performance industrial ozone generators:
supply with mains frequency (50 or 60 Hz) PA1 supply with medium frequency (200-2000 Hz)
Supply with mains frequency, which can only be used for ozone generators with small power densities q (power per active area), is very simple and consists, in principle, of only a regulating transformer and a high-voltage transformer. The power consumption of the ozone generator can be varied by regulating the voltage.
In ozone generators which are supplied with medium frequency, the mains voltage is converted to direct current by means of a controlled rectifier and is subsequently converted to medium frequency square-wave current with the aid of an inverter. This current, with associated voltage, is then transformed to the values necessary for operation of the ozone generator with the aid of a high-voltage transformer. A direct current choke between the rectifier and the inverter serves as an energy store and as an isolation between the low-frequency part and the medium-frequency part. In DE-B1 No. 2,525,059 (claim 1), specific attention was drawn to the fact that the direct current choke must have very high inductance so that square-wave current is always available to the ozone generator, since this improves the ozone yield. The power consumption of the ozone generator can be adjusted by varying the direct current, the frequency, the square-wave width (pulse width) or by a combination of the above.
One disadvantage of both types of supply is caused by the poor power factor of the ozone generator (cos .PSI.=0.4 . . . 0.5), which means that the supplies must be oversized. The effects of the poor power factor on the mains can, if necessary, be reduced by compensation on the mains side.
In a further device for the generation of ozone (German Offenlegungsschrift No. 2,122,041), in which two electrodes, which are connected to the poles of an alternating current source, are isolated from one another by a solid dielectric and a gas path, an inductance is inserted between the alternating current source and the electrodes. This inductor has a magnitude such, on the one hand, the natural frequency of the resonating circuit formed by the inductance in combination with the capacitance of the solid dielectric is below the operation frequency of the alternating current source, but, on the other hand, the inductance is so dimensioned that, together with the capacitance formed by the series connection of the dielectric and the gas path, it forms a resonating circuit with natural frequency above the operating frequency of the alternating current source.
In this fashion, use of a correspondingly large inductance means that the natural frequency of the system, when ignited, is lower than the operating frequency and that the harmonic content which is produced is considerably reduced. Thus, the capacitance of the ozone generator changes in total twice within one period of the applied alternating voltage, and the natural frequency of the system is first above and then below the operating frequency. If the inductance is designed correctly, a voltage is achieved at the ozone generator which is significantly above the voltage at the high-voltage source, maybe even more than twice that voltage, and an almost sinusoidal current curve is thereby produced. The harmonics in the current disappear almost completely, and a favorable load of the high-voltage source is obtained.
The compensation, provided in known devices, of the capacitive load of the voltage source is only effective in a comparatively small power density range. In addition, the proposed dimensioning of the inductance fails in ozone generators which are supplied by rectifiers.